This invention relates to dissolution testing machines capable of measuring the dissolution rate of chemicals from tablets or pellets. Such machines are, in particular, used in the pharmaceutical industry in connection with measuring the controlled rate of release of drugs.
In the past, two main standard methods have been used to conduct experiments on the rate of release of chemicals. In the first, the tablets, capsules, pellets or the like (hereinafter called `pellets`), are placed in the bottom of a standard container, and a paddle of standard shape is rotated about a vertical axis in a standard position in the container. However, the tendency is for the pellets to form a heap in the bottom of the container directly below the paddle, and the solution formed tends to maintain a gradient with the highest concentration at the bottom and the lowest at the top. Although standardized, as between tests, such an apparatus does not provide a true indication of rate of dissolution of the pellets when taken internally by a patient.
In the second method, the pellets are placed inside a perforated basket of generally cylindrical shape, which basket is itself rotated about its central longitudinal axis in the liquid. However, the tendency then is to form a film of chemical in solution around the pellets, with a higher concentration of solution within the basket than outside it. An increase in the speed of rotation may increase the dissolution rate, but may also cause abrasion of the pellets by the basket mesh, which thus falsifies the results in an opposite direction.
A third unofficial method employs a rotating bottle, in effect mounted on an arm of a rotating wheel in a vertical plane, so that the bottle is tipped upside down once in every revolution. However, since the bottle must be liquid tight during this operation, it becomes very difficult to extract samples for testing at different time intervals, and the process is inconvenient and labor intensive.